Without limiting the scope of the invention, its background is described in connection with current methods of forming electrical connections to high-dielectric-constant materials on semiconductor microcircuits.
DRAMs are used in many digital electronic devices and are most commonly used for computer memory. The ever increasing need for more memory in a computer has driven the demand for high density DRAMs. DRAMs generally use a capacitor as a data storage device, and it is the capacitor in these devices that is becoming the largest user of precious circuit real estate. Achieving higher density capacitor circuits will require higher storage capacitance for a given area on the integrated circuit. Generally, total storage capacitance is related to the surface area of the electrode in contact with the capacitor dielectric, and the dielectric constant of the material between the electrodes. The current method generally utilized to achieve higher capacitance per area on a microcircuit is to increase the capacitor surface area/unit area by increasing the topography, such as in trench and stack capacitors using conventional SiO.sub.2 or SiO.sub.2 /Si.sub.3 N.sub.4 as the dielectric. This approach becomes very difficult in terms of manufacturability for devices such as the 256 Mbit and 1 Gbit DRAMs.
An alternative approach is to use a material for the capacitor dielectric that has a higher dielectric constant which will increase the total storage capacitance without a corresponding increase in circuit area. Integrated circuits which include capacitors will require such materials with advanced dielectrics to obtain higher densities. As used herein, the term "advanced dielectric" means a material having a dielectric constant greater than about 50 at device operating temperature. Many materials, such as (Ba,Sr)TiO.sub.3 (BST), have advanced dielectric constants which are generally much higher than the dielectric materials used in standard microelectronic devices. Various metals and metallic compounds, and typically noble metals such as Pt and conductive oxides such as RuO.sub.2, have been proposed as the electrodes for these advanced dielectric materials. To be useful in electronic devices, however, reliable electrode structures and methods must be devised which do not diminish the beneficial properties of these high-dielectric-constant materials.